from __future__ import annotations

import re
from html import escape
from typing import Dict, Iterable, List, Optional, Tuple

import bleach
from markdown_it import MarkdownIt
from mdit_py_plugins.footnote import footnote_plugin
from mdit_py_plugins.tasklists import tasklists_plugin
from mdit_py_plugins.deflist import deflist_plugin
from mdit_py_plugins.admon import admon_plugin
from mdit_py_plugins.anchors import anchors_plugin
from flask import url_for

from app.utils.slugs import slugify


# Build a MarkdownIt renderer with useful plugins
_md = (
    MarkdownIt("commonmark", {"linkify": True})
    .use(footnote_plugin)
    .use(tasklists_plugin, enabled=True, label=True)
    .use(deflist_plugin)
    .use(admon_plugin)
    # Use only supported options here to avoid version mismatches
    .use(anchors_plugin, permalink=True, max_level=6, slug_func=slugify)
)

# Bleach sanitization configuration
ALLOWED_TAGS = [
    # Basic text
    "p", "div", "span", "br", "hr", "blockquote", "pre", "code",
    # Headings
    "h1", "h2", "h3", "h4", "h5", "h6",
    # Lists
    "ul", "ol", "li", "dl", "dt", "dd",
    # Tables
    "table", "thead", "tbody", "tr", "th", "td",
    # Inline
    "em", "strong", "kbd", "sup", "sub", "abbr",
    # Links and images
    "a", "img",
]
ALLOWED_ATTRS = {
    "*": ["class", "id", "title"],
    "a": ["href", "name", "target", "rel"],
    "img": ["src", "alt", "title", "width", "height", "loading"],
}
ALLOWED_PROTOCOLS = ["http", "https", "mailto", "tel", "data"]  # data for images (pasted)


class WikiIndex:
    """
    Simple index for resolving [[WikiLinks]] by title, alias, or slug.
    """
    def __init__(self):
        self._map: Dict[str, Dict] = {}

    @staticmethod
    def _norm(key: str) -> str:
        return key.strip().lower()

    def add(self, *, id: str, title: str, slug: str, aliases: Iterable[str] = ()):
        keys = [title, slug, *list(aliases)]
        for k in keys:
            n = self._norm(k)
            if n and n not in self._map:
                self._map[n] = {"id": id, "title": title, "slug": slug}

    def resolve(self, key: str) -> Optional[Dict]:
        return self._map.get(self._norm(key))


def build_wiki_index(notes: Iterable) -> WikiIndex:
    idx = WikiIndex()
    for n in notes:
        idx.add(id=n.id, title=n.title, slug=n.slug, aliases=getattr(n, "aliases", []))
    return idx


def _rewrite_attachment_paths(md_text: str) -> str:
    """
    Turn relative markdown links/images to attachments (attachments/... or ./attachments/...)
    into absolute app URLs (/attachments/...) so they work from any route.
    """
    # Replace ![alt](attachments/...) and [text](attachments/...) patterns
    def repl(m: re.Match) -> str:
        prefix = m.group(1)  # ]( or ](./ or ](../ etc)
        path = m.group(2)
        # Normalize to /attachments/<path>
        clean = re.sub(r"^(\./|/)?attachments/", "", path)
        return f"{prefix}/attachments/{clean}"

    pattern = re.compile(r"(\]\()(\.?/?attachments/[^\)]+)")
    text = pattern.sub(repl, md_text)
    # Images
    img_pattern = re.compile(r"(!\[[^\]]*\]\()(\.?/?attachments/[^\)]+)")
    text = img_pattern.sub(repl, text)
    return text


def _wikilink_to_md_link(wikilink: str, idx: WikiIndex) -> Tuple[str, Optional[str]]:
    """
    Convert a single [[...]] to a markdown [text](url) if resolvable.
    Returns (replacement_text, resolved_id or None).
    Supports [[Note]], [[Note|Alias]], [[Note#Heading]], [[Note#Heading|Alias]].
    """
    inner = wikilink.strip()[2:-2]  # remove [[ ]]
    # Split alias part
    if "|" in inner:
        target_part, alias_text = inner.split("|", 1)
    else:
        target_part, alias_text = inner, None

    # Handle heading fragment
    if "#" in target_part:
        target_title, header = target_part.split("#", 1)
    else:
        target_title, header = target_part, None

    target_title = target_title.strip()
    alias_text = alias_text.strip() if alias_text else None

    hit = idx.resolve(target_title)
    link_text = alias_text or (hit["title"] if hit else target_title)
    if hit:
        href = url_for("notes.notes_view", note_id=hit["id"])
        if header:
            href = f"{href}#{slugify(header)}"
        return f"[{link_text}]({href})", hit["id"]
    else:
        # Unresolved — return a stylized placeholder anchor that won't navigate
        safe_label = escape(target_title)
        if header:
            safe_label += f"#{escape(header)}"
        disp = escape(alias_text) if alias_text else safe_label
        html = f'<span class="text-warning/90 underline decoration-dotted" title="Unresolved wikilink">[[{disp}]]</span>'
        return html, None


def _rewrite_wikilinks(md_text: str, idx: WikiIndex) -> Tuple[str, List[str], List[str]]:
    """
    Replace all [[...]] links. Returns (new_text, resolved_ids, unresolved_texts)
    """
    resolved: List[str] = []
    unresolved: List[str] = []

    def repl(m: re.Match) -> str:
        w = m.group(0)
        replacement, note_id = _wikilink_to_md_link(w, idx)
        if note_id:
            resolved.append(note_id)
        else:
            unresolved.append(w)
        return replacement

    # Match anything between [[ ]] non-greedy
    pattern = re.compile(r"\[\[(.+?)\]\]")
    new_text = pattern.sub(repl, md_text)
    return new_text, resolved, unresolved


def sanitize_html(html: str) -> str:
    cleaned = bleach.clean(
        html,
        tags=ALLOWED_TAGS,
        attributes=ALLOWED_ATTRS,
        protocols=ALLOWED_PROTOCOLS,
        strip=True,
    )
    # Make external links open safely
    cleaned = bleach.linkify(
        cleaned,
        callbacks=[],
        skip_tags=["pre", "code"],
        parse_email=True,
    )
    return cleaned


def render_markdown(body_md: str, all_notes: Iterable) -> dict:
    """
    Render Markdown with:
    - Obsidian-style [[WikiLinks]] (resolved by title/alias/slug).
    - Attachment path rewriting to /attachments/...
    - Markdown-it-py with useful plugins.
    - Bleach sanitization.
    Returns:
      {
        "html": "<sanitized html>",
        "outbound_note_ids": [...],
        "unresolved_wikilinks": ["[[...]]", ...]
      }
    """
    idx = build_wiki_index(all_notes)

    # Preprocess: wikilinks -> markdown links (or styled unresolved spans), attachments -> absolute
    text_with_attachments = _rewrite_attachment_paths(body_md or "")
    text_with_links, resolved_ids, unresolved = _rewrite_wikilinks(text_with_attachments, idx)

    # Render to HTML
    raw_html = _md.render(text_with_links)

    # Sanitize
    safe_html = sanitize_html(raw_html)

    return {
        "html": safe_html,
        "outbound_note_ids": resolved_ids,
        "unresolved_wikilinks": unresolved,
    }